Fix the conversion lifetime by reorganizing the code

Author: EliahKagan

zng/cmake.rs

@@ -17,23 +17,23 @@ pub fn build_zlib_ng(target: &str, compat: bool) {
     if target.contains("riscv") {
         // Check if we should pass on an explicit boolean value of the WITH_RVV build option.
         // See: https://github.com/zlib-ng/zlib-ng?tab=readme-ov-file#advanced-build-options
-        match env::var_os("RISCV_WITH_RVV")
-            .and_then(|v| v.to_str())
-            .map(|s| s.trim().to_uppercase().as_ref())
-        {
-            Some("OFF" | "NO" | "FALSE" | "0") => {
-                // Force RVV off. This turns off RVV entirely, as well as the runtime check for it.
-                // This is not usually necessary, but can be useful for building binaries portable
-                // to systems that do not support RVV but where auto-detection fails to identify
-                // this (as in https://github.com/zlib-ng/zlib-ng/issues/1705).
-                cmake.define("WITH_RVV", "OFF");
+        if let Ok(value) = env::var("RISCV_WITH_RVV") {
+            let value = value.trim().to_uppercase();
+            match value.as_str() {
+                "OFF" | "NO" | "FALSE" | "0" => {
+                    // Force RVV off. This turns off RVV entirely, as well as the runtime check for it.
+                    // This is not usually necessary, but can be useful for building binaries portable
+                    // to systems that do not support RVV but where auto-detection fails to identify
+                    // this (as in https://github.com/zlib-ng/zlib-ng/issues/1705).
+                    cmake.define("WITH_RVV", "OFF");
+                }
+                "ON" | "YES" | "TRUE" | "1" => {
+                    // Try to use RVV, but still don't do so if a runtime check finds it unavailable.
+                    // This has the same effect as omitting WITH_RVV, unless it has already been set.
+                    cmake.define("WITH_RVV", "ON");
+                }
+                _ => {}
             }
-            Some("ON" | "YES" | "TRUE" | "1") => {
-                // Try to use RVV, but still don't do so if a runtime check finds it unavailable.
-                // This has the same effect as omitting WITH_RVV, unless it has already been set.
-                cmake.define("WITH_RVV", "ON");
-            }
-            _ => { }
         }
     }
     if target == "i686-pc-windows-msvc" {